Polarizable amines and polymides for optical alignment of liquid crystals

ABSTRACT

The present invention relates to amine compositions and the preparation of polyimides. The polyimides can be used for inducing alignment of a liquid crystal medium with polarized light in liquid crystal display elements.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of application Ser. No. 09/080,883 filedMay 18, 1998, now U.S. Pat. No. 6,043,337, which is aContinuation-in-Part of U.S. application Ser. No. 08/859,404, filed May20, 1997 now U.S. Pat. No. 6,084,057.

This invention was made with United States Government support underAgreement No. MDA972-93-2-0014 awarded by ARPA. The United StatesGovernment has certain rights in the invention.

BACKGROUND OF THE INVENTION

The present invention relates to compositions useful for inducingalignment of a liquid crystal medium with polarized light and liquidcrystal display elements.

Most liquid crystal devices, including displays, have a finite pre-tiltangle, controlled, for instance, by the mechanical buffing of selectedpolymeric alignment layers. Liquid crystal. molecules in contact withsuch a layer align parallel to the buffing direction, but not exactlyparallel to the substrate. The liquid crystal molecules are slightlytilted from the substrate, for instance, by about 0.5-15°. For mostdisplay applications, a finite and uniform pre-tilt angle of the liquidcrystal is desirable. For other display applications requiringpredominately homeotropic alignment of liquid crystals, a much higherpre-tilt angle is desired, for instance, 85-89.9°. In these cases,controlling the pre-tilt by a mechanical rubbing process is verydifficult.

A new process for aligning liquid crystals with polarized light wasdisclosed in U.S. Pat. No. 4,974,941 entitled “Process of Aligning andRealigning Liquid Crystal Media”. Controlling the pre-tilt angle ofliquid crystals in contact with optical alignment layers. whilemaintaining high uniformity of alignment, is an important requirementfor optical alignment materials. Continuing effort has been directed tothe development of compositions for optical alignment of liquid crystalsand liquid crystal displays.

SUMMARY OF THE INVENTION

The present invention provides polarizable fluorinated amines of thegeneral formula I

P—L_(f)—A—(NH₂)_(q)  I

wherein A is a divalent or trivalent organic moiety, L_(f) is a divalentorganic radical comprising at least four fluorinated carbon atoms; P isa polar group comprising a Pi electron system containing at least oneheteroatom selected from the group N, O and S; and q is 1 to 2.

The invention also provides a polyamic acid composition which is thereaction product of an amine component and a tetracarboxylic dianhydridecomponent which comprises at least one structural element of each offormulas IV and V

wherein X₄ is an electron withdrawing group having a positive σ, A is atrivalent organic moiety, P is a polar group comprising a Pi electronsystem containing at least one heteroatom selected from the group N, O,and S, and L_(f) consists essentially of:

—X—(CH₂)_(n)—(CF₂)_(p)—(CH₂)_(n)—X—

wherein —(CF₂)_(p)— is a straight chain or branched chain perfluoroalkylradical, p is 4 to 20, X is selected from the group consisting of—CH₂O—, —CH₂S—, —CH₂NR—, —O—, —S—, —NR— and a covalent bond, wherein Ris a C₁-C₄ hydrocarbon, n is up to 4 and M is a tetravalent organicradical derived from said tetracarboxylic dianhydride containing atleast two carbon atoms, no more than two carbonyl groups of thedianhydride being attached to any one carbon atom of the tetravalentradical.

The invention further provides polyimides derived from the polyamicacids and liquid crystal display elements made with the polyimidecompositions.

BRIEF DESCRIPTION OF THE FIGURE

FIG. 1 is a summary of the synthesis of polarizable fluorinated amines.

FIG. 2 illustrates the experimental setup for exposing substrates topolarized UV light.

FIG. 3 illustrates the construction of a liquid crystal display element.

DETAILED DESCRIPTION OF THE INVENTION

The polarizable amines of the present invention have been found to beparticularly useful in the preparation of polyamic acids and the relatedpolyimides. As used herein, as appropriate, the term “polyimide” alsoincludes the corresponding precursor polyamic acid unless otherwiseindicated. The polyimides, in turn, can be used to align liquidcrystals. The polyimide compositions provide high uniformity ofalignment and can induce a finite pre-tilt to liquid crystals that areoptically aligned with polarized light.

The polarizable fluorinated amines of the present invention, when usedin the optical alignment of a liquid crystal medium adjacent to asurface of an optical alignment layer, and particularly the polar groupwithin these amines, provides controllable pre-tilt in the liquidcrystal.

The polar group P can comprise a two atom system such as a carbonylgroup; a three atom Pi system, for example, an enol ether, enamine,etc.; a four atom Pi system, for example an α, β-unsaturated nitrile,ketone, etc.; a five atom Pi system, for example, an α, β-unsaturatedester, an aromatic ring containing a heteroatom, for example, apyridine, indole or benzofuran ring; an aromatic ring with a heteroatomlinked through a covalent bond such as a phenoxy or anilino group, a1,4-substituted phenylene Pi system wherein one or both substituents areheteroatoms; an aromatic ring conjugated to a two, three, four or fiveatom Pi system, for example, a cinnamate ester; or a 1,4-substitutedphenylene Pi system wherein one of the substituents is a heteroatom andthe other a two, three, four or five atom Pi system, for example a4-aminobenzonitrile group.

Preferred polar P groups include photoactive groups that undergo achemical change upon irradiation with light. Preferred P groups that arephotoactive are diaryl ketone, cinnamate, stilbene, arylazo,aryl(diazo), aryl(triazo) and aryl(tetraazo) radicals.

Other preferred polar P groups include liquid crystal radicalscomprising a diad, triad or tetraad liquid crystal radical. Examplesinclude 4,4′substituted biphenyl, 4,4′substituted phenyl benzoate,4,4′-substitute biphenyl benzoate and 4,4′substituted phenylbiphenylcarboxylate radicals.

Other preferred P groups include aromatic rings selected from the group

wherein X₃ is selected from the group —N(R₂)₂, —CN, —NO₂, wherein R₂ isselected from the group consisting of H and C₁-C₄ hydrocarbon chains andt is up to 4.

Within the polarizable amines, diamines are preferred, that is, thosecompounds in which q is 2.

Preferable polarizable fluorinated amines of this invention are diaminesof structure III:

wherein Ar′ is selected from the group:

wherein t is up to 4; X, n and p are as described below, and X₃ isselected from the group —N(R₂)₂, —CN, —NO₂, wherein R₂ is selected fromthe group consisting of H and C₁-C₄ hydrocarbon chain.

In the polarizable fluorinated amines, preferred are those in whichL_(f) is a moiety of the formula:

—X—(CH₂)_(n)—(CF₂)_(p)—(CH₂)_(n)—X—

wherein —(CF₂)_(p)— is a straight chain or branched chainperfluoroalykyl radical, p is 4 to 20, X is selected from the groupconsisting of a covalent bond, —CH₂O—, —CH₂S—, —CH₂NR—, —O—, —S— and—NR—, wherein R is a C₁-C₄ hydrocarbon, and n is up to 4. Of these,those in which X is —O—, p is 4 to 12 and n is 1 to 3 have been found tobe particularly satisfactory, and are accordingly preferred. Alsopreferred are those amines in which A is an aromatic ring selected fromthe group consisting of:

Preferred polyamic acids and polyimides of the invention are thereaction product of at least one tetracarboxylic dianhydride at leastone polarizable fluorinated diamine and at least one monoamine of theformula:

X₁—(CF₂)_(p)—(CH₂)_(n)—X—Ar—NH₂

wherein Ar is selected from the group

X is selected from the group consisting of —O—, —S— and —NR— and acovalent bond, wherein R is a C₁-C₄ hydrocarbon, X₁ is selected from Hand F, n is 0 to 4 and p is 6 to 20, wherein the monoamine comprisesbetween 1 mol % and 5 mol % of the amine component and the polarizablefluorinated diamine comprises 2 mol % to 12 mol % of the aminecomponent. Preferably, X is selected from the group —O— and —NR— and nis 1 to 4.

Preferred monoamines are those wherein Ar is phenyl, X is —O—; n is 1 to2; p is 6 to 18 and X₁ is F. A specific monoamine that is most preferredis 4-(1H, 1H-dihydroperfluorooctyloxy)benzeneamine.

Generally, as described in Estes et al., U.S. Pat. No. 5,186,985, amonoamine would be used only as an end-capping entity, and thereforelimit the length of the molecule. However, for use in optical alignmentprocesses, lower molecular weight polymers offer the advantage of highermobility. Thus, the probability of achieving a desired photochemicalreaction upon irradiation with polarized light increases.

Synthesis of Monoamines

Monoamines are readily available by reduction of the corresponding nitroderivatives with tin (II) chloride or catalytic reduction with hydrogenand 5% palladium on carbon.

The nitro intermediates are readily available by nucleophilicdisplacement of 4-fluoronitrobenzene by a variety of monofunctionalfluorinated alcohols and amines. Specific conditions for this reactionare outlined in the experimentals below. However, in general, afluorinated alcohol or amine is stirred with the 4-fluoronitrobenzene ina polar aprotic solvent such as dimethylformamide, N-methylpyrrolidoneor dimethylacetamide, in the presence of an organic or inorganic basesuch as triethylamine, potassium carbonate or potassium hydroxide.Usually, heating to 80° C. will facilitate the reaction.

Monofunctional fluorinated alcohols are commercially available. Forinstance, 1H,1H,5H-octafluoro-1-pentanol, 1H,1H,7H-perfluoro-1-heptanol,1H,1H-perfluoro-1-octanol, 1H,1H,2H,2H-perfluoro-1-octanol,1H,1H,2H,2H-perfluoro-1-decanol1H,1H,2H,2H-perfluoro-1-dodecanol,1H,1H2H,2H-perfluoro-9-methyl-1-decanol are available from PCR Inc.,Gainesville, Fla. 32602 or Oakwood Products, Inc., West Columbia, S.C.29169. Other monofunctional fluorinated alcohols are readily availableby well known synthetic procedures. For instance,1H,1H-perfluoro-1-tetradecanol, 1H,1H-perfluoro-1-dodecanol,1H,1H-perfluoro-1-decanol, 1H,1H,-perfluoro-1-nonanol,1H,1H,9H-perfluoro-1-nonanol, 1H,1H-perfluoro-1-heptanol are availableby reduction of the corresponding acids or acid chlorides with potassiumborohydride according to the procedure of Bilibin, et al., in Macromol.Chem. Phys., 197, 1021-1029, (1966). Alternatively, a mixture of sodiumborohydride and aluminum chloride can be used to accomplish thereduction to the alcohol. Other fluorinated alcohols are available bythe known radical addition reaction of perfluoroiodides toω-alkene-1-ols as described in Wang, et al., J. Polym. Prepr. (Am Chem.Soc., Div. Polym. Chem.), 37 #2, 815 (1996) or Hopken, et al., NewPolym. Mater., 2, 339.

A monofunctional fluorinated amine commercially available is1H,1H-perfluoro-1-octylamine. Other monofunctional fluorinated aminesare readily available by well known synthetic procedures. For instance,the ethyl esters of the fluorinated acids listed above are readilyconverted to amides by treatment with ammonia or primary amines. Theamides can be readily reduced with diborane in tetrahydrofuran toproduce primary and secondary amines. For instance,1H,1H-perfluoro-1-tetradecylamine, 1H,1H-perfluoro-1-dodecylamine,1H,1H-perfluoro-1-decylamine, 1H,1H,-perfluoro-1-nonylamine,1H,1H,9H-perfluoro-1-nonylamine, 1H,1H-perfluoro-1-heptylamine areavailable by reduction of the corresponding primary amides.N-methyl-1H,1H-perfluoro-1-tetradecylamine,N-methyl-1H,1H-perfluoro-1-dodecylamine,N-methyl-1H,1H-perfluoro-1-decylamine,N-methyl-1H,1H,-perfluoro-1-nonylamine,N-methyl-1H,1H,9H-perfluoro-1-nonylamine,N-methyl-1H,1H-perfluoro-1-heptylamine are available by reduction of thecorresponding N-methyl amides.

Polarizable fluorinated amines of formula I can be readily prepared bythe synthesis outlined in FIG. 1. Starting material which can be used isa fluorinated or partially fluorinated diol, diamine, dithiol, or acompound of mixed functionality, for instance, an aminoalcohol. Thefluorinated difunctional compound is treated to react selectively at onesite with the polar moiety, P, for instance, by nucleophilicdisplacement of a halogen from the polar moiety. Usually, a polaraprotic solvent such as dimethylformamide, N-methylpyrrolidone, methylethyl ketone, acetone, cyclopentanone, cyclohexanone ordimethylacetamide, in the presence of an organic or inorganic base suchas triethylamine, potassium carbonate, sodium carbonate or potassiumhydroxide is used in the first step. A large excess of the difunctionalcompound is usually used to insure formation of the desiredmonofunctional intermediate. Usually, heating to about 80° C. issufficient to facilitate the reaction, but lower and higher temperaturescan be used. The resulting monofunctional intermediate is then treatedto react the second functional site, for instance by nucleophilicdisplacement of halogen from a 2,4-dinitrochlorobenzene. Usually, apolar aprotic solvent such as dimethylformamide, N-methylpyrrolidone,methyl ethyl ketone, acetone, cyclopentanone, cyclohexanone ordimethylacetamide, in the presence of an organic or inorganic base suchas triethylamine, potassium carbonate, sodium carbonate or potassiumhydroxide is used in the second step. Usually heating to 80° C. issufficient to facilitate the reaction, but lower and higher temperaturescan be used. The nitro and dinitro analogs are then reduced with tin(II) chloride or catalytic reduction with hydrogen and 5% palladium oncarbon. Specific reaction conditions for this reduction are described inthe examples.

Starting materials for the synthesis of polarizable fluorinated aminesare available commercially. For instance, commercially availabledifunctional fluorinated alcohols are2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol,3,3,4,4,5,5,6,6-octafluoro-1,8-octanediol and1H,1H,10H,10H-hexadecafluoro-1,10-decanediol, available from OaklandProducts, West Columbus, S.C. 29169. The corresponding diacids are alsocommercially available. These diacids can be converted to N-methylamides and reduced with diborane in tetrahydrofuran to produce N-methyldiamine derivatives. In this manner,N,N′-dimethyl-2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediamine,N,N′-dimethyl-3,3,4,4,5,5,6,6-octafluoro-1,8-octanediamine in a similarand manner N,N′-dimethyl-1H,1H,10H,10H-hexadecafluoro-1,10-decanediaminecan be prepared.

Other starting materials are available by synthesis. For instance,3,3,4,4,5,5,6,6,7,7,8,8-dodecafluoro-1,10-decanediamine,3,3,4,4,5,5,6,6-octafluoro-1,8-diamine,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10-hexadecafluoro-1,12-dodecanediamineare available from the corresponding azides using the proceduresdescribed by Malik, et al., Journal Organic Chemistry, 56, 3043 (1991).

Branched chain fluorinated starting materials are available bysynthesis. Telomers of perfluoropropylene withα,ω-diiodoperfluoroalkanes are converted to branched-chain difunctionalcondensation monomers. Reaction of these telomers with ethylene giveα,ω-diiodoethylperfluoroalkanes as described by Baum, et al., JournalOrganic Chemistry, 59, 6804 (1994). Thus, available are1,10-diiodo-1H,1H,2H,2H,11H,11H,12H,12H-perfluoro-3-methyldecane,1,12-diiodo-1H,1H,2H,2H,11H,11H,12H,12H-perfluoro-3-methyldodecane andan isomeric mixture of1,12-diiodo-1H,1H,2H,2H,11H,11H,12H,12H-perfluorodimethyldodecane. Theiodo functional ends can be used directly in alkylation reactionssimilar to that described in Example 9. The diiodides can be convertedto diols by reaction with fuming sulfuric acid. The diiodides can beconverted to diamines by conversion to azides and reduction usingconventional procedures as described by Baum et al. Thus, available are1H,1H,2H,2H,11H,11H,12H,12H-perfluoro-3-methyl-1,12-dodecanediol,1H,1H,2H,2H,11H,11H,12H,12H-perfluoro-3-methyl-1,12-dodecanediamine,1H,1H,2H,2H,11H,11H,12H,12H-perfluoro-3-methyl-1,12-decanediol,1H,1H,2H,2H,11H,11H,12H,12H-perfluoro-3-methyl-1,12-decanediamine, andisomeric mixtures of1H,1H,2H,2H,11H,11H,12H,12H-perfluorodimethyl-1,12-dodecanediol,1H,1H,2H,2H,11H,11H,12H,12H-perfluorodimethyl-1,12-dodecanediamine.

The polarizable fluorinated amines can be a blend of monoamines anddiamines. Preferably, the monoamine comprises between 1 mol % and 12 mol% of the amine component. Specific diamines of the present invention areillustrated in Table 1.

TABLE 1 Polarizable Fluorinated Diamines 1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

The term “alignment layer” hereinafter refers to the layer of materialon the surface of a substrate that controls the alignment of a liquidcrystal layer in the absence of an external field. A “conventionalalignment layer” hereinafter refers to an alignment layer that will onlyalign a liquid crystal layer via processing other than optical means.For example, mechanically buffed polyimides, evaporated silicon dioxide,and Langmuir-Blodgett films, have all been shown to align liquidcrystals.

“Optical alignment layer” hereinafter refers to an alignment layer thatcontains anisotropically absorbing molecules that will induce alignmentof liquid crystals after exposure with polarized light. Opticalalignment layers can be processed by conventional means, such asmechanical rubbing, prior to or after exposure to polarized light. Theanisotropically absorbing molecules of the optical alignment layersexhibit absorption properties with different values when measured alongaxes in different directions. The anisotropic absorbing moleculesexhibit absorption bands between about 150 nm and about 2000 nm. Theanisotropically absorbing molecules of the optical alignment layer canbe covalently bonded within a main chain polymer, they can be covalentlybonded as side groups to a main polymer chain, they can be present asnonbonded solutes in a polymer, or they can be in the adjacent liquidcrystal layer as a solute and adsorbed on the surface of a normalalignment layer to give an optical alignment layer.

Preferred optical alignment layers have absorbance maxima of about from150 to 1600 nm. More preferable optical alignment layers have absorbancemaxima of about from 150 nm to 800 nm. Most preferable optical alignmentlayers for the present invention have absorbance maxima of about from150 and 400 nm and especially about from 300 to 400 nm.

Anisotropically absorbing molecules that can be used in opticalalignment layers and various methods for forming optical alignmentlayers are discussed in U.S. Pat. No. 5,731,405 entitled “Process andMaterials for Inducing Pre-tilt in Liquid Crystals and Liquid CrystalDisplays,” hereby incorporated by reference.

Polymers especially useful and preferred in the optical process of thisinvention are polyimides. Polyimides are known for their excellentthermal and electrical stability properties and these properties areuseful in optical alignment layers for liquid crystal displays. Thepreparation of polyimides is described in “Polyimides”, D. Wilson, H. D.Stenzenberger, and P. M. Hergenrother Eds., Chapman and Hall, New York(1990). Typically polyimides are prepared by the condensation of oneequivalent of a diamine with one equivalent of a dianhydride in a polarsolvent to give a poly(amic acid) prepolymer intermediate.

The poly(amic acid) is typically formulated to give a 1 to 30 wt %solution. The condensation reaction is usually performed between roomtemperature and 150° C. The prepolymer solution is coated onto a desiredsubstrate and thermally cured at between 180 and 300° C. to complete theimidization process. Alternatively, the poly(amic acid) prepolymer ischemically imidized by addition of a dehydrating agent to form apolyimide polymer.

In preparing polyimides for optical alignment layers the molar ratio ofdiamine to dianhydride usually is 1:1, but can vary between 0.8:1 to1:1.2. The preferred ratio of diamine to dianhydride is between 0.9:1and 1:1.1.

The invention further embodies polyamic acids prepared from polarizablefluorinated amines of structure I and at least one tetracarboxylicdianhydride and the corresponding polyimides derived therefrom.

As the tetracarboxylic dianhydride component, diaryl ketonetetracarboxylic dianhydrides especially useful for the invention arethose having the following structure:

wherein X₂ is independently selected from th e group H, Cl, F, Br, R₁,R₁O—, wherein R₁ is independently selected from C₁-C₃ perfluorinatedalkyl chain, C₁-C₃ partially perfluorinated alkyl chain and C₁-C₈hydrocarbon chain, m is 1 or 0; Z is selected from the group —S—, —O—,—SO₂—, —CH₂—, —C(CF₃)₂—, —C(O)—, —CH₂CH₂—, —NR— and a covalent bondwherein R is a C₁-C₄ hydrocarbon chain. The more preferred diarylketones are 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and2,2′-dichloro-4,4′5,5′-benzophenonetetracarboxylic dianhydride. The mostpreferred benzophenone dianhydride for this invention is3,3′,4,4′-benzophenonetetracarboxylic dianhydride.

A wide variety of other dianhydrides can be used in forming polyimidesuseful in the invention. Specific examples of the tetracarboxylicdianhydride component include aromatic dianhydrides such as pyromelliticdianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride,1,2,5,6-naphthalenetetracarboxylic dianhydride,1,4,5,8-naphthalenetetracarboxylic dianhydride,3,3′4,4′-biphenyltetracarboxylic dianhydride,2,3,2′,3′-biphenyltetracarboxylic dianhydride,bis(3,4-dicarboxyphenyl)ether dianhydride,bis(3,4-dicarboxyphenyl)diphenylsulfone dianhydride,bis(3,4-dicarboxyphenyl)methane dianhydride,2,2-bis(3,4-dicarboxyphenyl)propane dianhydride,1,1,1,3,3,3-hexafluoro-2,2-bis(3,4-dicarboxyphenyl)propane Other diarylketones dianhydrides that are useful in the process of the invention,wherein m is 1, are the polycyclic diaryl ketone dianhydrides describedby Pfeifer, et al., in U.S. Pat. No. 4,698,295 and hereby incorporatedby reference. Another diaryl ketone dianhydride that can be useful is5,5′-[carbonylbis(4,1-phenyleneoxy)]bis-1,3-isobenzofuranone, StructureVI

In one preferred embodiment the invention is a composition which is thereaction product of at least one diaryl ketone tetracarboxylicdianhydride, an amine component comprising at least two diamines, apolarizable fluorinated diamine and a second diamine, and at least onemonoamine of the formula shown above.

Preferred are polyamic acids and polyimide compositions wherein thepolarizable fluorinated diamine is of the formula III and morespecifically, a polyimide composition wherein the diaryl ketonetetracarboxylic dianhydride of formula II is preferred.

A most preferred polyimide composition is that wherein the diaryl ketonetetracarboxylic dianhydride is 3,3′,4,4′-benzophenonetetracarboxylicdianhydride; the polarizable fluorinated diamine is of formula IIIwherein Ar′ is phenyl, t is 4, X is —O—, n is 1, p is 4, X₃ is selected.from the group —N(R₂)₂, —CN, and —NO₂ and wherein R₂ is selected from Hand C₁-C₄ hydrocarbon chain; and the monoamine is4-(1H,1H-dihydroperfluorooctyloxy)benzeneamine; wherein and themonoamine comprises 1 mol % to 5 mol % and the polarizable fluorinateddiamine comprises 2 mol % to 12 mol % of the amine component.

Another embodiment of the present invention is a polyimide compositionwhich is the reaction product of at least one tetracyclic dianhydrideand an amine component comprising at least two diamines including adiaminobenzophenone and a polarizable fluorinated diamine of formulaIII, and at least one monoamine of the formula shown above, wherein andthe monoamine comprises 1 mol % to 5 mol % and the polarizablefluorinated diamine comprises 2 mol % to 12 mol % of the aminecomponent.

Alicyclic tetracarboxylic dianhydrides refer to dianhydrides that arecomprised either partially or in whole of saturated carbocyclic rings.The alicyclic tetracarboxylic dianhydrides impart useful solubilityproperties to polyimides comprising them. Alicyclic tetracarboxylicdianhydrides suitable for the invention are5-(2,5-dioxotetrahydro)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride, commercially available from Chriskev, Inc.,2,3,5-tricarboxycyclopentaneacetic acid dianhydride, available viasynthesis by oxidation of dicyclopentadiene with nitric acid;1,2,3,4-cyclobutanetetracarboxylic dianhydride,1,2,3,4-butanetetracarboxylic dianhydride, and the like.

A preferred polyimide composition is that wherein the dianhydridecomponent comprises a diaryl ketone tetracarboxylic dianhydride offormula II and an alicyclic tetracarboxylic dianhydride. More preferableis a polyimide wherein the alicyclic dianhydride is between 1-50 mol %of the dianhydride component. Most preferable is a polyimide wherein thealicyclic dianhydride is5-(2,5-dioxotetrahydro)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride.

A most preferred polyamic acid composition for optical alignment layersis the reaction product of an amine component and a tetracarboxylicdianhydride component which comprises at least two structural elementsof the following formula

wherein X₄ is an electron withdrawing group having a positive σ, A is atrivalent organic moiety, P is a polar group comprising a Pi electronsystem containing at least one heteroatom selected from the group N, O,and S; and L_(f) consists essentially of:

—X—(CH₂)_(n)—(CF₂)_(p)—(CH₂)_(n)—X—

wherein —(CF₂)_(p)— is a straight chain or branched chain perfluoroalkylradical, p is 4-20, X is selected from the group consisting of —CH₂O—,—CH₂S—, —CH₂NR—, —O—, —S—, —NR— and a covalent bond, wherein R is aC₁-C₄ hydrocarbon, n is up to 4; and M is a tetravalent organic radicalderived from said tetracarboxylic dianhydride containing at least twocarbon atoms, no more than two carbonyl groups of the dianhydride beingattached to any one carbon atom of the tetravalent radical.

The propensity for an organic substituent to donate or withdraw electrondensity from a electronic system is described by the Hammett equation.J. March describes the Hammett equation in detail in “Advanced OrganicChemistry, Reactions, Mechanism, and Structure”, McGraw-Hill,Publishers, New York 1977, p. 252-255. A positive value of σ indicatesan electron-withdrawing group and a negative value an electron-donatinggroup. Preferred polyamic acid compositions for optical alignmentmaterials have polyamic acid backbones wherein electron withdrawinggroups in 2-substituted-1,4-benzenediamine moieties are present togetherwith fluorinated polarizable diamines. The presence of both structuralelements allows a balance to be achieved between high pre-tilt and highanchoring energy.

More preferred polyamic acids are wherein X₄ is selected from the groupCN, —CF₃, F, Cl, Br, I, —NO₂, —CO₂R₂, and —CON(R₂)₂, wherein R₂ is H ora C₁-C₄ hydrocarbon; A is an aromatic ring selected from the groupconsisting of:

P is selected from the group of:

wherein X₃ is selected from the group —N(R₂)₂, —CN, —NO₂ and t is equalup to 4; within L_(f), X is selected from —CH₂O— and —O—, p is 4-12 andn is 1 to 3; and M is

wherein X₂ is independently selected from the group H, Cl, F, Br, R₁,R₁O—, wherein R₁ is independently selected from C₁-C₃ perfluorinatedalkyl chain, C₁-C₃ partially perfluorinated alkyl chain and C₁-C₈hydrocarbon chain, m is 1 or 0; Z is selected from the group —S—, —O—,—SO₂—, —CH₂—, —C(CF₃)₂—, —C(O)—, —CH₂CH₂—,—NR— and a covalent bondwherein R is a C₁-C₄ hydrocarbon chain; and the acid groups are ortho tothe amide linkages.

Specific diamines useful in this invention are readily available fromcommercial sources. For instance, 2-(trifluoromethyl)-1,4-benzenediamineis available from PCR Inc. (P.O. Box 1466, Gainesville, Fla. 32602);2,5-diaminobenzonitrile is available from Frinton Laboratories (P.O. Box2428, Vineland, N.J. 08360); 2-nitro-1,4-phenylenediamine is availablefrom Aldrich Chemical Co., 1001 West Saint Paul Ave., Milwaukee, Wis.53233; 2-chloro-1,4-phenylene diamine is available from ChemetallChemical Products Co., 50 Valley Rd., Berkley Heights, N.J. 07922. Otheruseful diamines such as 2-fluoro-1,4-phenylene diamine,2-bromo-1,4-phenylene diamine, methyl 2,5-diaminobenzoate, and2,5-diaminobenzamide are available by synthesis.

To prepare the optical alignment layers of this invention, poly(amicacid) solutions or preimidized polyimide solutions are coated ontodesired substrates. Coating is usually accomplished with about from 2 to30 wt % solids. Any conventional method can be used to coat thesubstrates including brushing, spraying, spin-casting, dipping orprinting. The coated substrates are typically heated in an oven under aninert atmosphere, for instance nitrogen or argon, at elevatedtemperature usually not exceeding 300° C. and preferably at or below180° C. for about from 1 to 12 hours, preferably for about 2 hours orless. The heating process removes the solvent carrier and can be used tofurther cure the polymer. For instance, the poly(amic) acid films arethermally cured to generate polyimide films.

The optical alignment layers are exposed to polarized light to inducealignment of liquid crystals. By “polarized light” is meant light thatis elliptically polarized such that the light is more polarized alongone axis (referred to as the major axis) versus the orthogonal axis(referred to as the minor axis). The preferred polarization is linearlypolarized light where the light is polarized mostly along one axis (themajor axis) with little or no polarization component along the minoraxis. In this invention the polarized light has one or more wavelengthsof about from 150 to 2000 nm and preferably of about from 150 and 1600nm and more preferably about from 150 to 800 nm. Most preferably, thepolarized light has one or more wavelengths of about from 150 to 400 um,and especially about from 300 to 400 nm. A preferred source of light isa laser, e.g., an argon, helium neon, or helium cadmium. Other preferredsources of light are mercury arc deuterium and quartz tungsten halogenlamps, xenon lamps and black lights in combination with a polarizer.Polarizers useful in generating polarized light from nonpolarized lightsources are interference polarizers made from dielectric stacks,absorptive polarizers and reflective polarizers based on Brewsterreflection. With lower power lasers or when aligning small alignmentregions, it can be necessary to focus the light beam onto the opticalalignment layer.

By “exposing” is meant that polarized light is applied to the entireoptical alignment layer or to a portion thereof. The light beam can bestationary or rotated. Exposures can be in one step, in bursts, inscanning mode or by other methods. Exposure times vary widely with thematerials used, etc., and can range from less than 1 msec to over anhour. Exposure can be conducted before or after contacting the opticalalignment layer with the liquid crystal medium. Exposing can beaccomplished by linearly polarized light transmitted through at leastone mask having a pattern or with a beam of linearly polarized lightscanned in a pattern. Exposing also can be accomplished usinginterference of coherent optical beams forming patterns, i.e.,alternating dark and bright lines.

Exposure energy requirements vary with the formulation and processing ofthe optical alignment layer prior and during exposure. For example,materials that possess high glass transition temperatures can havehigher energy density requirements for optical alignment. Whereas,material systems designed to have a low glass transition temperatureprior to exposure can have lower energy density requirements. Apreferred range of exposure energy is about from 0.001 to 2000 J/cm².More preferred is the range of about from 0.001 to 100 J/cm² and mostpreferred range of exposure energy is about from 0.001 to 5 J/cm². Lowerexposure energy is most useful in large scale manufacturing of opticalalignment layers and liquid crystal display elements. Lower exposureenergy also minimizes the risk of damage to other materials on thesubstrates.

The efficiency of the alignment process, and the exposure energyrequired, can be further impacted by heating, beyond that inherent inthe “exposing” step. Additional heating during the exposing step can beaccomplished by conduction, convection or radiant heating, or byexposure to unpolarized light. Additional heating can increase themobility of the molecules during exposure and improve the alignmentquality of the optical alignment layer. Additional heating is not arequirement of the process of the invention but can give beneficialresults.

The quality of alignment and electrical properties of the liquid crystalcell assembled from exposed substrates can be improved by heating thesubstrates after exposure but prior to assembly of the cell. Thisadditional heating of the substrates is not a requirement of the processbut can give beneficial results.

Exposing also can consist of two or more exposure steps wherein theconditions of each step such as angle of incidence, polarization state,energy density, and wavelength are changed. At least one of the stepsmust consist of exposure with linearly polarized light. Exposures canalso be localized to regions much smaller than the substrate size tosizes comparable to the entire substrate size. A preferred method ofdual exposing comprises a two step process of:

(a) exposing at least one optical alignment layer to polarized light ata normal incidence, and

(b) exposing the optical alignment layer to polarized light at anoblique incidence.

Another preferred method of dual exposing comprises a two step processof:

(a) exposing said optical alignment layer to polarized light of a firstdirection of linear polarization of the incident light and

(b) exposing said optical alignment layer to polarized light of a seconddirection of linear polarization of the incident light.

Still another preferred method of dual exposing comprises a two stepprocess of:

(a) exposing said optical alignment layer to polarized light of a firstdirection of linear polarization of the incident light, and

(b) exposing said optical alignment layer to polarized light of a seconddirection of linear polarization of the incident light, at an obliqueincidence.

Yet another preferred method of dual exposing comprises a two stepprocess of:

(a) exposing said optical alignment layer to polarized light of a firstdirection of linear polarization of the incident light at an obliqueincidence, and

(b) exposing said optical alignment layer to polarized light of a seconddirection of linear polarization of the incident light, at an obliqueincidence.

Applying a liquid crystal medium to the optical alignment can beaccomplished by capillary filling of a cell, by casting of a liquidcrystal medium onto an optical alignment layer, by laminating apreformed liquid crystal film onto an optical alignment layer or byother methods. Preferred methods are capillary filling of a cell andcasting of a liquid crystal medium onto an optical alignment layer.Optical alignment layers are pre-exposed to polarized light or they areexposed after contacting the liquid crystal medium.

A cell can be prepared by using two coated substrates to provide asandwiched layer of liquid crystal medium. The pair of substrates canboth contain optical alignment layers or a conventional alignment layer(e.g., mechanically buffed) can be used as the second alignment layercomprising the same or a different polymer.

As liquid crystal substances used for liquid crystal optical elements,nematic liquid crystal substances, ferroelectric liquid crystalsubstances, etc. are usable. Useful liquid crystals for the inventiondescribed herein include those described in U.S. Pat. No. 5,032,009 andnew superfluorinated liquid crystals available from EM Industries,Hawthorne N.Y.

The exposed optical alignment layer induces alignment of a liquidcrystal medium at an angle + and −θ with respect to the direction of thelinear polarization of the incident light beam and along the plane ofthe optical alignment layer. One skilled in the art will recognize thatthe process of the instant invention allows control of the alignment ofa liquid crystal medium in any desired direction within the plane of theoptical alignment layer by controlling the conditions of the polarizedlight exposure. Preferrably the liquid crystal medium is aligned at anangle + and −θ, where θ is equal to about 90° to the polarizationdirection.

A liquid crystal display element made by the process of the instantinvention is composed of an electrode substrate having at least oneoptical alignment layer, a voltage-impressing means and a liquid crystalmaterial. FIG. 3 illustrates a typical liquid crystal display element,comprising a transparent electrode 13 of ITO (indium-tin oxide) or tinoxide on a substrate 12 and optical alignment layers 14 formed thereon.The optical alignment layers are exposed to polarized light of awavelength or wavelengths within the absorption band of theanisotropically absorbing molecules. A spacer concurrently with asealing resin 15 is intervened between a pair of optical alignmentlayers 14. A liquid crystal 16 is applied by capillary filling of thecell and the cell is sealed to construct a liquid crystal displayelement. Substrate 12 can comprise an overcoat film such as aninsulating film, a color filter, a color filter overcoat, a laminatedpolarizing film etc. These coatings and films are all considered part ofthe substrate 12. Further, active elements such as thin filmtransistors, a nonlinear resistant element, etc. can also be formed onthe substrate 12. These electrodes, undercoats, overcoats, etc. areconventional constituents for liquid crystal display elements and areusable in the display elements of this invention. Using the thus formedelectrode substrate, a liquid crystal display cell is prepared, and aliquid crystal substance is filled in the space of the cell, to preparea liquid crystal display element in combination with avoltage-impressing means.

The L_(f) radical is derived from difunctional perfluorinated andpartially fluorinated hydrocarbons.

1,16-Dibromo-5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12-hexadecafluorohexadecaneis first prepared by the following procedure:

1,8-diiodoperfluorooctane (65.4 g, Fluorochem, Inc., Azusa, Calif.91702), 3-buten-1-ol (14.4 g) and azoisobutylnitrile (AIBN, 0.3 g) isheated to 80° C. for 5 hrs. Tributyltin hydride (64.0 g) and additionalAIBN (0.3 g) are added and heating is continued for 5 hr.5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12-Hexadecafluoro-1,16-hexadecanediolis purified by kugelrohr distillation under reduced pressure.

5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12-Hexadecafluoro-1,16-hexadecanediol(27.3 g) and 48% aqueous hydrobromic acid is heated to 80° C. for 24hrs. The mixture is diluted with water, extracted with ethyl ether, andwashed several times with water. The extracts are dried (MgSO₄) andconcentrated. The material is kugelrohr distilled under reduced pressureto give1,16-dibromo-5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12-hexadecafluorohexadecane.

3,3,4,4,5,5,6,6,-octafluoro-1,8-octanediamine is first prepared by theprocedures described by Malik et al., Journal Organic Chemistry, 56,3043 (1991).

The examples of the invention use a fluorinated monoamine that wasprepared by synthesis. 4-(1H,1H-perfluorooctyloxy)benzeneamine was madeby the following procedure:

A mixture of 4-fluoronitrobenzene (141.1 g), 1H,1H-perfluorooctanol(420.1 g), and potassium hydroxide (79.2 g) in 1-methyl-2-pyrrolidinone(1.0 L) was stirred at room temperature for 16 h under a nitrogenatmosphere. The mixture was extracted from aqueous solution andconcentrated to give 4-(1H,1H-perfluorooctyloxy)nitrobenzene which wasrecrystallized and reduced with hydrogen and 5% Pd/C. The crude productwas Kugelrohr distilled and recrystallized to give4-(1H,1H-perfluorooctyloxy)benzeneamine as crystals, mp 49.1-50.2° C.

EXAMPLE 1

This example illustrates synthesis of a polarizable fluorinated diamine1.

A mixture of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol (78.63 g, AldrichChemical Co., Milwaukee, Wis.), 1-fluoro-2,4-dinitrobenzene (18.6 g),triethyl amine (42 mL) and acetone (100 mL) was heated to 80° C. for 1.5hr. After aqueous workup the excess hexanediol was removed by Kugelrohrdistillation and the dimer by-product was removed by crystallization.The residual oil was treated with pentafluorobenzonitrile (19.3 g),triethyl amine (15.3 mL) and acetone (100 mL) and heated to reflux for 4h. Aqueous workup followed by extraction gave4-[6-(2,4-dinitrophenoxy)-2,2,3,3,4,4,5,5-octaflurohexyloxy]-2,3,5,6-tetrafluorobenzonitrileas an orange oil.

The oil was reduced with tin chloride dihydrate (140.4 g), concentratedhydrochloric acid (97.5 mL) and ethanol (300 mL) at 35-40° C. for 4.25hr. Aqueous workup with potassium hydroxide (240 g) and extraction gavea crude diamine that was purified by repeated recrystallization to givediamine 1 (mp 97-98.2° C.).

EXAMPLE 2

This example illustrates synthesis of a polarizable fluorinated diamine2.

A mixture of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol (15.7 g),4-fluorobenzonitrile (2.42 g), potassium carbonate (1.36 g) andN-methylpyrrolidone (50 mL) was heated to 80° C. for 18 hrs. The mixturewas diluted with water and extracted with ether. The extracts werewashed with water and brine, and dried (Mg SO₄) and the excess diolremoved by distillation. The pot residue was taken up in ethanol,cooled, and a by-product removed by filtration. The ethanol was removedto give a yellow solid (mp 95-97° C.).

The solid (5.1 g) was treated with 2,4-dinitrochlorobenzene (3.4 g),potassium carbonate (3.8 g) and NMP (20 mL) for about 24 hrs. at 72-76°C. The mixture was diluted with water, extracted with ethyl ether,washed with water and concentrated to give a yellow oil (8.3 g).Chromatography and recrystallization from ethanol gave4-[6-(2,4-dinitrophenoxy)-2,2,3,3,4,4,5,5-octaflurohexyloxy]benzonitrile,2.0 g, mp 89.0-90.6° C.

4-[6-(2,4-Dinitrophenoxy)-2,2,3,3,4,4,5,5-octaflurohexyloxy]benzonitrile(1.85 g) in ethanol (50 mL) was agitated with 5% palladium on carbon at30 psi hydrogen atmosphere for 3 hrs. The solution was filtered throughglass fiber mats and the ethanol removed. The red oil was purified bychromatography to give 0.30 g of diamine 2 as a colorless oil.

EXAMPLE 3

1H,1H,10H,10H-hexadecafluoro-1,10-decandediol (Oakland Products, WestColumbus, S.C. 29169) is processed as described in Example 1 to give thediamine 3.

EXAMPLE 4

3,3,4,4,5,5,6,6-octafluoro-1,8-octanediol (Oakland Products, WestColumbus, S.C. 29169) is processed as described in Example 1 to give thediamine 4.

EXAMPLE 5

1-(6-hydroxy-2,2,3,3,4,4,5,5-octafluorohexyloxy)-2,4-dinitrobenzene (3.7g) was treated with pentafluoronitrobenzene (2.21 g) and triethylamine(0.96 g) in NMP (5 mL) for 18 hrs at room temperature. The mixture wasdiluted with water, acidified with hydrochloric acid, and extracted withethyl ether. The extracts were washed with water, dried (Mg SO₄),concentrated and purified by chromatography to give4-[6-(2,4-dinitrophenoxy)-2,2,3,3,4,4,5,5-octaflurohexyloxy]-2,3,5,6-tetrafluoronitrobenzene(5.0 g) as an oil.

4-[6-(2,4-Dinitrophenoxy)-2,2,3,3,4,4,5,5-octaflurohexyloxy]-2,3,5,6-tetrafluoronitrobenzene(5.0 g) was treated with tin chloride dihydrate as described inExample 1. Purification of the product by chromatography gave diamine 5(1.2 g, mp at room temperature).

EXAMPLE 6

This example illustrates synthesis of a polarizable fluorinated diamine6.

A mixture of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol (7.86 g) wastreated with pentafluoronitrobenzene (2.13 g) and triethylamine (1.39mL) in NMP (15 mL) at room temperature for 1 hr. The mixture was dilutedwith water, acidified with acetic acid, and extracted with ethyl ether.The extract was washed with water and brine; dried (MgSO₄) andconcentrated. Excess diol was removed by distillation and the residualoil purified by chromatography to give4-(6-hydroxy-2,2,3,3,4,4,5,5-octafluorohexyloxy)tetrafluoronitrobenzene(3.06 g).

A solution of the4-(6-hydroxy-2,2,3,3,4,4,5,5-octafluorohexyloxy)-2,3,5,6-tetrafluoronitrobenzene(2.0 g) in ethanol (50 mL) was treated with tin (II) chloride dihydrate(9.9 g) at 60° C. for 18 hrs. under a nitrogen atmosphere. The mixturewas diluted with ice water, basified with potassium hydroxide (10.1 g)in water (80 mL) and extracted with ethyl ether. The extracts werewashed with water and brine, dried (K₂CO₃), and concentrated to an oil.The oil was purified by chromatography to give4-(6-Hydroxy-2,2,3,3,4,4,5,5-octafluorohexyloxy)-2,3,5,6-tetrafluorobenzeneamineas an oil (1.77 g).

The4-(6-hydroxy-2,2,3,3,4,4,5,5-octafluorohexyloxy)-2,3,5,6-tetrafluorobenzeneamine(0.70 g) was treated with methyl iodide (0.41 mL) in NMP (4 mL) andsodium bicarbonate (0.27 g) at 50° C. followed by further addition ofmethyl iodide (0.41 mL portions) after 2, 18 and 20 hrs. At 22 hrs. themixture was diluted with water and extracted with ethyl ether. Theextracts were washed with water and brine, dried (K₂CO₃), andconcentrated to the dimethylamino derivative as an oil (0.76 g).

N,N-Dimethyl-4-(6-hydroxy-2,2,3,3,4,4,5,5-octafluorohexyloxy)-2,3,5,6-tetrafluorobenzeneamine(1.05 g) was treated with 1-chloro-2,4-dinitrobenzene (0.51 g) andpotassium carbonate (0.35 g) in NMP (5 mL) at 80° C. for 21.5 hrs. Themixture was diluted with water and extracted with ethyl ether. Theextracts were washed with water and brine, dried (K₂CO₃), andconcentrated to an orange oil. The oil was purified by chromatography togiveN,N-dimethyl-4-[6-(2,4-dinitrophenoxy)-2,2,3,3,4,4,5,5-octaflurohexyloxy]-2,3,5,6-tetrafluorobenzeneamine(1.05 g) as an oil.

The dinitro compound was reduced with tin chloride dihydrate asdescribed above and the resulting oil purified by chromatography andrecrystallization to give the diamine 6 (0.07 g, mp 52.0-53.2° C.).

EXAMPLE 7

This example illustrates formation of a polarizable fluorinated diamine7.

A mixture of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol (7.86 g),4-fluoroacetophenone (1.36 g), NMP (10 mL), and potassium carbonate(4.14 g) is heated to 95-100° C. for 48 hrs. The mixture is firtherprocessed as described in Example 1 to provide4-(6-hydroxy-2,2,3,3,4,4,5,5-octafluorohexyloxy)acetophenone.

4-(6-Hydroxy-2,2,3,3,4,4,5,5-octafluorohexyloxy)acetophenone (3.78 g),2,4-dinitrochlorobenzene (2.42 g) potassium carbonate (2.76 g) and NMP(15 mL) are heated to 75-80° C. for 24 hrs. The solution is furtherprocessed as described in Example 2 to give4-[6-(2,4-dinitrophenoxy)-2,2,3,3,4,4,5,5-octaflurohexyloxy]acetophenone.

4-[6-(2,4-Dinitrophenoxy)-2,2,3,3,4,4,5,5-octaflurohexyloxy]acetophenone(6.44 g) and sodium hydroxide solution (20 g 20 wt %) is treated withsodium hypochlorite (56 mL, 5.25 wt % solution) in 1,2-dimethoxyethane(200 mL) at 50-60° C. until the acetophenone disappears as indicated bymonitoring with thin layer chromatography. Heating is continued for 2hrs and the solvent is removed under reduced pressure. The mixture isdiluted with water and excess hypochlorite neutralized with sodiumbisulfite. The solution is acidified with hydrochloric acid andextracted with ethyl ether. The extracts are washed with brine, dried(MgSO₄) and concentrated give4-[6-(2,4-dinitrophenoxy)-2,2,3,3,4,4,5,5-octaflurohexyloxy]benzoicacid.

4-[6-(2,4-Dinitrophenoxy)-2,2,3,3,4,4,5,5-octaflurohexyloxy]benzoic acid(6.46 g), toluene (30 mL), oxalyl chloride (2.0 g) and 1 drop ofanhydrous dimethyl formamide is stirred for 16 hrs. at room temperatureunder a nitrogen atmosphere. Excess oxalyl chloride and toluene (10 mL)is removed by reduced pressure distillation. The remaining acid chloridesolution is added to a solution of 4-cyanophenol (1.31 g), toluene (20mL) and triethylamine (1.5 g) and the mixture is stirred 24 hrs. at50-60° C. under a nitrogen atmosphere. The solution is diluted withwater, slightly acidified with hydrochloric acid, and extracted withtoluene-ethyl ether. The extracts are washed with water and brine, dried(MgSO₄), concentrated, and purified by chromatography to give the4-cyanophenyl4-[6-(2,4-dinitrophenoxy)-2,2,3,3,4,4,5,5-octaflurohexyloxy]benzoate.

4-Cyanophenyl4-[6-(2,4-dinitrophenoxy)-2,2,3,3,4,4,5,5-octaflurohexyloxy]benzoate(7.63 g), in ethanol (100 mL) is agitated with 5% palladium on carbon(0.8 g) at 40 psi hydrogen atmosphere for 8 hrs. The solution isfiltered through glass fiber mats and the ethanol removed. The productis purified by chromatography to give the diamine 7.

EXAMPLE 8

This example illustrates formation of polarizable fluorinated diamine 8.

1H,1H,10H,10H-Hexadecafluoro-1,10-decandediol (13.86 g),4-fluorobenzophenone (2.0 g), potassium carbonate (4.14 g) and NMP (10mL) is heated to 95-100° C. for 48 hrs. The mixture is firther processedas described in Example 1 to provide4-(10-hydroxy-2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorodecyloxy)benzophenone.

A solution of4-(10-Hydroxy-2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorodecyloxy)benzophenone(6.42 g), 2,4-dinitrochlorobenzene (2.42 g) potassium carbonate (2.76 g)and NMP (15 mL) is heated to 75-80° C. for 24 hrs. The solution isfurther processed as described in Example 2 to give4-[10-(2,4-dinitrophenoxy)-2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorodecyloxy]benzophenone.

4-[10-(2,4-Dinitrophenoxy)-2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorodecyloxy]benzophenone(8.08 g) is treated with tin (II) chloride dihydrate as described inExample 1 and purified by chromatography to give diamine 8.

EXAMPLE 9

This example illustrates formation of polarizable fluorinated diamine 9.

A solution of1,16-dibromo-5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12-hexadecafluorohexadecane(20.16 g), 4′-hydroxy-4-cyanobiphenyl (2.05 g), potassium carbonate(2.07 g) and acetone (30 mL) is refluxed for 8 hrs. The acetone isremoved under reduced pressure and the residue diluted with water andextracted with ethyl ether. The extracts are washed with water andbrine, dried (MgSO₄), concentrated, and purified by chromatography togive4′-(16-bromo-,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12-hexadecafluorohexadecyloxy)-4-cyanobiphenyl.

4′-(16-Bromo-,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12-hexadecafluorohexadecyloxy)-4-cyanobiphenyl(7.96 g), 2,4-dinitrophenol (2.21 g), potassium carbonate (1.65 g) andNMP (10 mL) is heated to 80-85° C. under a nitrogen atmosphere for 18hrs. The solution is diluted with water and extracted with ethyl ether.The extracts are washed with water and brine, dried (MgSO₄),concentrated, and purified by chromatography to give4′-[16-(2,4-dinitrophenoxy)-,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12-hexadecafluorohexadecyloxy)-4-cyanobiphenyl.

The above dintiro compound (8.99 g) is reduced with palladium on carbonas described in Example 7 to give diamine 9.

EXAMPLE 10

This example illustrates formation of polarizable fluorinated diamine10.

A mixture of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol (7.86 g),4-fluorobenzaldehyde (1.24 g), NMP (10 mL), and potassium carbonate(4.14 g) was heated to 95-100° C. for 48 hrs. The mixture was furtherprocessed as described in Example 1 to provide4-(6-hydroxy-2,2,3,3,4,4,5,5-octafluorohexyloxy)benzaldehyde.

4-(6-hydroxy-2,2,3,3,4,4,5,5-octafluorohexyloxy)benzaldehyde (3.66 g)2,4-dinitrochlorobenzene (2.42 g) potassium carbonate (2.76 g) and NMP(15 mL) are heated to 75-80° C. for 24 hrs. The solution is furtherprocessed as described in example 2 to give4-[6-(2,4-dinitrophenoxy)-2,2,3,3,4,4,5,5-octaflurohexyloxy]benzaldehyde.

To a mixture of trimethylsilyl diethylphosphonoacetate (2.97 g) inanhydrous tetrahydrofuran (100 mL) at 0° C. is added 1.6 M solution ofbutyllithium in hexane (6.9 mL). The reaction is stirred for 2 hrs. atroom temperature and then treated with4-[6-(2,4-dinitrophenoxy)-2,2,3,3,4,4,5,5-octaflurohexyloxy]benzaldehyde(5.32 g) in anhydrous tetrahydrofuran (30 mL). The mixture is stirredfor a further 2 hrs., diluted with water and extracted with ethyl ether.The extracts are washed with water and brine, dried (MgSO₄),concentrated, and purified by crystallization to give4-[6-(2,4-dinitrophenoxy)-2,2,3,3,4,4,5,5-octaflurohexyloxy]cinnamicacid. The acid is converted to the methyl ester by treatment withdiazomethane in ether solution.

The resulting dinitro methyl cinnamate ester (6.04 g) is reduced withtin (II) chloride as described in Example 7 and is purified bychromatography to give diamine 10.

EXAMPLE 11

This example illustrates formation of polarizable fluorinated diamine11.

1H,1H,10H,10H-Hexadecafluoro-1,10-decandediol (13.86 g),2,3,4,5,6-pentafluorobenzophenone (2.72 g), potassium carbonate (4.14 g)and NMP (10 mL) is heated to 80° C. until the starting benzophenonedissipates by TLC analysis. The mixture is further processed asdescribed in Example 1 to provide4-(10-hydroxy-2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorodecyloxy)-2,3,4,5,6-pentafluorobenzophenone.

A solution of4-(10-Hydroxy-2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorodecyloxy)-2,3,4,5,6-pentafluorobenzophenone(7.14g), 2,4-dinitrochlorobenzene (2.42 g) potassium carbonate (2.76 g) andNMP (15 mL) is heated to 75-80° C. for 24 hrs. The solution is furtherprocessed as described in example 2 to give4-[10-(2,4-dinitrophenoxy)-2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorodecyloxy]-2,3,4,5,6-pentafluorobenzophenone.

4-[10-(2,4-Dinitrophenoxy)-2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorodecyloxy]-2,3,4,5,6-pentafluorobenzophenone(8.90 g) is treated with tin (II) chloride dihydrate as described inExample 1 and purified by chromatography to give diamine 11.

EXAMPLE 12

A mixture of 3,3,4,4,5,5,6,6,-octafluoro-1,8-octanediamine (8.6 g),1-chloro-2,4-dinitrobenzene (2.0 g, 10 mmol), potassium carbonate (1.36g, 10 mmol) and N-methylpyrrolidone (50 mL, NMP) is heated to 80° C. for20 hrs. The mixture is diluted with water and extracted with ether. Theextracts are washed with water, concentrated and the excessoctanediamine removed by Kugelrohr distillation.

The residue is treated with pentafluorobenzonitrile (1.91 g, 10 mmol),triethyl amine (1.0 g, 10 mmol) and NMP (50 mL) at room temperature for75 minutes. The mixture is diluted with water and extracted with ethylether-tetrahydrofuran (4:1). The extracts are washed with water, dried(K₂CO₃) and concentrated. The resulting material is chromatographed togive4-[6-(2,4-dinitroanilino-3,3,4,4,5,5,6,6,-octafluorooctylamino]-2,3,5,6-tetrafluorobenzonitrile.

The benzonitrile is treated with tin chloride dihydrate (16.9 g, 75mmol) and ethanol (100 mL) at 35° C. for 24 hrs. The mixture is pouredinto ice water, basified with potassium hydroxide (12.6 g), andextracted with ethyl ether-tetrahydrofuran (3:1). The extracts arewashed with water and brine, dried (MgSO₄) and concentrated. Thematerial is chromatographed and recrystallized to give diamine 12.

EXAMPLE 13

This example illustrates the use of diamine 1 in a poly(amic acid)formulation and the use of the poly(amic acid) to prepare a polyimideoptical alignment layer for alignment of liquid crystals.

To a solution of 2-(trifluoromethyl)-1,4-benzenediamine (82.5 mg) anddiamine 1 (13.5 mg) in γ-butyrolactone (1.24 g) was added3,3′,4,4′-benzophenonetetracarboxylic dianhydride (161.1 mg) at roomtemperature under a nitrogen atmosphere. The mixture was stirred for 0.5hr and 4-(1H,1H-dihydroperfluorooctyloxy)benzeneamine (6.1 mg) was addedfollowed by stirring for 23 hrs. at room temperature. The mixture wasdiluted with γ-butyrolactone (3.76 g) before spinning optical alignmentlayers.

Two 0.9 inch by 1.2 inch by 1 millimeter thick borosilicate glasssubstrates with transparent indium-tin-oxide (ITO) electrode coatings(Donnelly Corp., Holland, Mich.) were spin-coated and cured with thepolyimide formulation to give optical alignment layers. Spin coating wasachieved by filtering the prepolymer solution through a 0.45 mm Teflonfilter membrane directly onto the surface of the clean ITO glasssubstrates. The coated ITO glass substrates were then spun at 2500 RPMfor 1 minute to produce uniform thin films. The resultant thin filmswere cured under nitrogen for 0.25 hrs. at 80° C. followed by 1 hr. at180° C.

FIG. 2 is a schematic of the experimental set-up used to expose thesubstrates. A laser beam of about 1 cm in diameter from laser 1,polarized along direction 2, entered a polarizing rotator and beamsplitter combination 3 and, upon exiting, two polarization components 6and 7 separated as they propagated away from 3. The wavelength range ofthe laser was 300-336 nm. By adjusting the polarizing rotator in 3, theratio of optical power in 6 and 7 can be adjusted and, in this case, theratio was adjusted to be 1:6. The total power in 6 and 7 was 500 mW.Mirrors 5 reflected 6 and 7 through cylindrical lenses 8 and 9 withfocal lengths of 5 cm and 10 cm, respectively. After passing throughcylindrical lenses 8 and 9, 6 and 7 were focused into lines of about 1cm×0.2 cm onto the substrate(s) 10. The separation between the twoparallel focused lines was about 1.5 mm. As depicted in FIG. 2, thesubstrates 10 were scanned perpendicular to the focused lines. Since thefocused line lengths of about 1 cm was smaller than the desired exposurearea, after scanning one time, the substrates were stepped 1.5 mmperpendicular to the scan direction (along the focused lines). The stepand scan 11 were repeated until the entire substrate area was exposed.The scan speed for this exposure was 0.75 mm/s.

A twisted nematic liquid crystal cell was constructed from the twoexposed coated substrates. Four micron spacers were mixed in with anepoxy and the epoxy mixture was placed at the edges of the coated sideon one exposed substrate. The second exposed substrate was placed on topof the first substrate such that the alignment layers were facing eachother and the respective background alignment directions wereperpendicular to each other. The substrates were pressed to a fourmicrometer spacing using clamps and the fiber spacer/epoxy mixture wasallowed to cure. Two spaces on opposite sides of the cell were leftunsealed so that the liquid crystal would fill the cell along thebisector between the alignment directions of the substrates. The cellwas placed in a vacuum and, subsequently, one unsealed opening on thecell was dipped into a nematic liquid crystal doped with chiralcompound. After filling, the cell was removed from the liquid crystaland vacuum, cleaned up, and the spaces sealed with epoxy. The cell wassubsequently heated above the nematic-isotropic transition of the liquidcrystal to remove any defects introduced during filling.

The cell was viewed between parallel and crossed polarizers on aphotographic light box. For the two polarizer configurations, thetransmission of the cell was consistent with a twisted nematicorientation of the liquid crystal and the cell gave a net uniformtwisted nematic alignment. The pre-tilt angle was measured using thecrystal rotation method to be approximately 1°.

EXAMPLE 14

This example further illustrates the use of diamine 1 in a poly(amicacid) formulation and the use of the poly(amic acid) to prepare apolyimide optical alignment layer for alignment of liquid crystals.

A mixture of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (70.9 g),2-(trifluoromethyl)-1,4-benzenediamine (34.86 g), diamine 1 (5.95 g),4-(1H,1H-perfluorooctyloxy)benzeneamine (5.40 g) and γ-butyrolactone(470 g) was stirred at room temperature for 24 h under a nitrogenatmosphere. The solution was diluted to a 10 wt % solution withγ-butyrolactone (585.0 g) and filtered through a 0.45 micron teflonmembrane filter and stored in a refrigerator under nitrogen until used.

The substrates were coated, processed and exposed as described inExample 13 and the exposure conditions were adjusted accordingly forthis formulation. The pre-tilt was measured to be approximately 2°.

EXAMPLE 15

This example further illustrates the use of diamine 1 in a poly(amicacid) formulation and the use of the poly(amic acid) to prepare apolyimide optical alignment layer for alignment of liquid crystals.

To a solution of 2-(trifluoromethyl)-1,4-benzenediamine (164.2 mg),4-(1H,1H-perfluorooctyloxy)benzeneamine (17.2 mg) and diamine 1 (27.1mg) in γ-butyrolactone (1.79 g) was added3,3′,4,4′-benzophenonetetracarboxylic dianhydride (290.0 mg) and5-(2,5-dioxotetrahydro)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride (26.4 mg) followed by stirring for 23 hr at room temperature.The mixture was diluted with γ-butyrolactone (8.17 g) before spinningoptical alignment layers.

The substrates were coated and processed as described in Example 13, theexposure conditions were adjusted accordingly for this formulation. Theresults were the same as Example 13 except that the pre-tilt wasmeasured to be approximately 2°.

EXAMPLE 16

This example further illustrates the use of diamine 1 in a poly(amicacid) formulation and the use of the poly(amic acid) to prepare apolyimide optical alignment layer for alignment of liquid crystals.

To a solution of 2-(trifluoromethyl)-1,4-benzenediamine (73.7 mg),4-(1H,1H-perfluorooctyloxy)benzeneamine (6.1 mg),4,4′diaminobenzophenone (10.6 mg) and diamine 1 (13.5 mg) inγ-butyrolactone (1.02 g) was added 3,3′,4,4′-benzophenonetetracarboxylicdianhydride (145.0 mg) and5-(2,5-dioxotetrahydro)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride (13.2 mg) followed by stirring for 23 hrs. at roomtemperature. The mixture was diluted with -butyrolactone (3.96 g) beforespinning optical alignment layers.

The substrates were coated and processed as described in Example 13, theexposure conditions were adjusted accordingly for this formulation. Theresults were the same as Example 13 except that the pre-tilt wasmeasured to be approximately 2°.

EXAMPLE 17

This example illustrates the use of diamine 5 in a poly(amic acid)formulation and the use of the poly(amic acid) to prepare a polyimideoptical alignment layer for alignment of liquid crystals.

To a solution of 2-(trifluoromethyl)-1,4-benzenediamine (83.6 mg) anddiamine 5 (13.3 mg) in γ-butyrolactone (1.80 g) was added3,3′,4,4′-benzophenonetetracarboxylic dianhydride (161.1 mg) at roomtemperature under a nitrogen atmosphere and the solution was stirred for23 hrs. at room temperature. The mixture was diluted withγ-butyrolactone (3.10 g) before spinning optical alignment layers.

The substrates were coated and processed as described in Example 13, theexposure conditions were adjusted accordingly for this formulation. Theresults were the same as Example 13 except that the pre-tilt wasmeasured to be approximately 0°. The cell showed very good uniformity ofalignment.

EXAMPLE 18

This example illustrates the use of diamine 6 in a poly(amic acid)formulation and the use of the poly(amic acid) to prepare a polyimideoptical alignment layer for alignment of liquid crystals.

To a solution of 2-(trifluoromethyl)-1,4-benzenediamine (83.6 mg) anddiamine 6 (14.0 mg) in γ-butyrolactone (1.30 g) was added3,3′,4,4′-benzophenonetetracarboxylic dianhydride (161.1 mg) at roomtemperature under a nitrogen atmosphere and the solution was stirred for23 hrs. at room temperature. The mixture was diluted withγ-butyrolactone (3.62 g) before spinning optical alignment layers.

The substrates were coated and processed as described in Example 13, theexposure conditions were adjusted accordingly for this formulation. Theresults were the same as Example 13 except that the pre-tilt wasmeasured to be approximately 0°. The cell showed very good uniformity ofalignment.

EXAMPLE 19

A mixture of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol (39.25 g),3,5-dinitrobenzyl chloride (10.8 g), potassium carbonate (20.7 g) andNMP (50 mL) was stirred at room temperature for 17 hr. After aqueousworkup the excess hexanediol was removed by kugelrohr distillation. Theresidue oil (18.2 g) was chromatographed on silica gel to give 17.6 gorange oil.

The orange oil (8.8 g) was treated with pentafluorobenzonitrile (6.36g), triethyl amine (4.0 g) and acetone (40 mL) and heated to 72° C. for3 hrs. Aqueous workup followed by extraction gave an oil that waspurified by chromatography to give4-[6-(3,5-dinitrobenzyloxy)-2,2,3,3,4,4,5,5-octafluorohexyloxy]-2,3,5,6-tetrafluorobenzonitrile(8.6 g).

The dinitro nitrile (3.1 g) was treated with tin chloride dihydrate(11.25 g) and ethanol (40 mL) and heated gradually to 80° C. for over1.66 hr. Aqueous base workup followed by extraction gave an oil that waspurified by chromatography and recrystallized from hexane-ethyl acetateto give diamine 13 (mp 82-83.5° C.).

EXAMPLE 20

To a solution of 2-(trifluoromethyl)-1,4-benzenediamine (79.2 mg),4-(1H,1H-dihydroperfluorooctyloxy)benzeneamine (12.3 mg) and diamine 13(13.9 mg) in γ-butyrolactone (0.72 g) was added3,3′,4,4′-benzophenonetetracarboxylic dianhydride (161.1 mg) at roomtemperature under a nitrogen atmosphere. The sidewall was rinsed withγ-butyrolactone (0.40 g) followed by stirring for 22.5 hr at roomtemperature. The mixture was diluted with γ-butyrolactone (5.26 g)before spinning optical alignment layers.

Substrates were coated and processed as described in Example 13. Theresults were the same as Example 13 except that the pretilt was measuredto be approximately 1.5°.

EXAMPLE 21

A mixture of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (6.44 g),2,5-diaminobenzonitrile (2.46 g), diamine 1 (0.541 g),4-(1H,1H-dihydroperfluorooctyloxy)benzeneamine (0.491 g) andγ-butyrolactone (40.0 g) was stirred at room temperature for 24 h undera nitrogen atmosphere. The solution was diluted to a 10 wt % solutionwith -butyrolactone (49.8 g) and filtered through a 0.45 micron teflonmembrane filter. The solution was diluted to 5 wt % solution and spincoated as described in Example 1.

Substrates were coated, processed and exposed as described in Example13. The results were the same as Example 13 except that the pre-tilt wasmeasured to be approximately 0.2°. The uniformity of alignment with thisformulation was better than that of Example 14.

We claim:
 1. A polarizable diamine of the general formulaP—L_(f)—A—(NH₂)_(q) wherein A is a divalent or trivalent organic moiety,P is a polar group comprising a Pi electron system containing at leastone heteroatom selected from the group N, O, and S; q is 2, and L_(f)consists essentially of: —X—(CH₂)_(n)—(CF₂)_(p)—(CH₂)_(n)—X— wherein—(CF₂)_(p)— is a straight chain or branched chain perfluoroalkylradical, p is 4-20, X is selected from the group consisting of acovalent bond, —CH₂O—, —CH₂S—, —CH₂NR—, —O—, —S— and —NR—, wherein R isa C₁-C₄ hydrocarbon, and n is up to
 4. 2. A polarizable amine of claim 1wherein A is an aromatic ring selected from the group consisting of:

q is 2, and P is selected from the group consisting of:

wherein -X₃ is selected from the group —N(R₂)₂, —CN, and —NO₂, t isequal to 0-4, and R₂ is selected from H and hydrocarbon chains of 1 to 4carbon atoms.
 3. A polyamic acid comprising the reaction product of anamine component and at least one tetracarboxylic dianhydride, whereinthe amine component comprises a polarizable amine of claim
 1. 4. Apolyimide derived from the polyamic acid of claim
 3. 5. A liquid crystaldisplay element made from a composition of a polyimide of claim 4.